calendardemo example incorrectly indicates that Journal Entries are supported on Symbian^3

Ideally the example examples/calendardemo disables Add Journal menu entry on platforms that do not support Journal Entries.

Test Case 1:

• start calendardemo application on a platform whose default backend does not supports journal entries ( symbian engine on Symbian)
• click Options menu entry
• verify Add Journal menu is not presented

Test Case 2:

• start calendardemo application on a platform whose default does supports journal entries ( memory engine on Linux)
• click Options menu entry
• verify Add Journal menu is present